Many work machines include hydraulic systems for running motors or extending and retracting cylinders. These hydraulic systems include pumps having rotating groups that wear over time and eventually fail. If the failure of a pump is catastrophic, substantial debris can be introduced into the hydraulic system causing damage to other components. If, however, an impending failure is predicted or sensed prior to catastrophic failure, the pump can be replaced before damage to other components is caused. The repair can also be scheduled at the most opportune time to reduce productivity losses during repair.
An exemplary rotating group is illustrated in FIG. 1. The rotating group shown is in an axial piston type pump having an external case drain. As a pump begins to wear, volumetric inefficiencies increase. These inefficiencies are typified by fluid leaks around the face of the slipper, the ball socket, the piston wall, the port plate barrel interface, and the displacement control device. The leaking fluid then exits the case through the external case drain. By sensing the flow of fluid through the case drain, an indication of the extent of leakage can be obtained. This information can then be used to estimate remaining pump life.
Many conventional flow meters, such as turbine or paddle wheel flow sensors, may cause substantial back pressure. This back pressure on the pump case causes a pressure differential between the outlet and inlet which tends to pull the slipper away from the piston. In addition, shaft seals can be damaged by excess back pressure. Furthermore, pump displacement controls designed to drain to the case can suffer deleterious effects from high back pressure. Thus flow sensors with significant back pressure would cause a premature destruction of the pump or difficulty in pump displacement control.
Without any method or apparatus for sensing the increasing inefficiencies as component wear progresses, impending failures cannot be easily predicted and thus the likelihood of catastrophic failures causing damage to other components increases substantially. Likewise, repairs cannot be scheduled for the most opportune time to reduce losses of productivity during repair. Similarly, the increased leakage leads to increased fuel consumption and decreased productivity which may not be otherwise detected.
The present invention is directed to overcoming one or more of the problems set forth above.